FIELD OF THE INVENTION
The present invention relates to a method of recovering ethylene oxide. More specifically, the present invention relates to a method comprising the following steps;
Introducing a reaction product gas containing ethylene oxide, obtained by the vapor phase catalytic oxidation of ethylene with oxygen over a silver catalyst, to an ethylene oxide absorption tower;
absorbing ethylene oxide in an absorbent containing propylene carbonate; and PA1 supplying the absorbent to a stripping tower to recover ethylene oxide by stripping and subsequent separation. PA1 1) excellent absorbing power per weight, preferably the same as or greater than water; PA1 2) low specific heat; PA1 3) lack of reactivity with ethylene oxide and by-products; PA1 4) does not solidify or deteriorate within the normal operating conditions of a plant; and PA1 5) high boiling point, and small stripping and splashing loss. PA1 bringing a mixed gas containing ethylene oxide into contact with an absorbent so as to cause the absorbent to absorb the ethylene oxide; and PA1 stripping and separating said ethylene oxide to recover it from said absorbent; PA1 characterized in that the absorbent contains propylene carbonate. PA1 1) the absorbing power per weight of propylene carbonate with respect to ethylene oxide is about 50% higher than that of water and about 40% higher than that of ethylene carbonate; PA1 2) the specific heat of propylene carbonate is low at 0.4 cal/g..degree.C., which is similar to ethylene carbonate; PA1 3) propylene carbonate is stable and has no direct reactivity with ethylene oxide, and further propylene carbonate is extremely stable against by-products such as aldehydes and acids which are produced in the ethylene oxidation step even more so than ethylene carbonate; and, PA1 4) since the solidifying point of propylene carbonate is -49.degree. C., there is no solidifying problem regarding actual operating conditions, and moreover, absorption of ethylene oxide can be carried out at 5 to 40.degree. C., which does not require high equipment costs. For those excellent properties, there is no generation of impurities which consume ethylene oxide such as ethylene glycol, and further it becomes possible to set up an ethylene oxide absorption and stripping system which reduces the heat recovery loss resulting from cooling absorbent at the time of transfer from the stripping step to the absorption step to about one-third compared with a system employing water. These and other objects, features and advantages of the present invention will become clearer from the following description of the preferred embodiment taken in conjunction with the accompanying drawings.